The game that has been occupying my attention in the last couple of weeks more than most is the old TSR Top Secret, the original one, not the later Top Secret/S.I. (which doesn't really interest me). I've been looking for modules for the game and adventures printed in Dragon magazine. I also discovered that there was a significant revision of the hand-to-hand combat rules in the 2nd printing (and the revision is an improvement on the original rules), and that there was a Top Secret Companion which collected many of the optional rules that Merle Rasmussen wrote originally for his column in Dragon. I've also surprised myself by how many issues of Dragon I own that had articles regarding the game.
There are a lot of good old-school elements of the game. Actions are governed by broad categories of competence (and, with the Companion, formal training courses), some of which are universal, such as general athletic ability and the ability to deactivate electronics and mechanical mechanisms, while others are more focused areas of knowledge, such as scientific knowledge or a knowledge of history. This allows a character to attempt actions even in areas in which he is untrained, and to make use of the general knowledge of the player freely. In a sense, there are two separate, but interlocking, skills systems in the game: attributes and areas of knowledge, and training courses. There are also prototypes of more "story" oriented rules presented as options, such as hero points (here called Fame Points and Fortune Points).
Less worthwhile, the combat system uses a variant of D&D's Armor Class system. Weapons are given a Projectile Weapon Value (PWV) or Hand Weapon Value (HWV). This affects the ability of the weapon to hit the opponent. Projectile weapons then cause damage on a fixed table, from 1 to 12 points, while hand-to-hand weapons use a more complex system (described below). Armor modifies damage, reducing it by a percentage, or nearly eliminating damage from weapons below a certain caliber. There are some suggestions of how to handle larger weaponry (machine guns and missiles, for instance) in a Dragon magazine article, but this is not official. Damage is inflicted on a value called "Life Level", which is based on the basic, rolled attributes of the character.
Hand-to-hand combat is divided into various types: non-trained, wrestling, boxing/swordplay (these use the same table), judo, and martial arts. Hand weapons add a damage modifier when using non-trained or boxing/swordplay combat. In the original version, boxing and swordplay were separate, and there was a knife fighting option as well, but the revised system is much better. In a combat round, one character is the attacker, the other the defender. The attacker chooses an attack type secretly (which also determines which damage chart to use in the case of a hit), while the defender chooses two defenses. These are cross-indexed on the tables, and a result determined. This generally consists of a miss or a hit, possibly with a damage modifier, but can also include holds, a change of roles (defender becomes attacker and vice versa), or other results.
Combat has a number of optional rules which can increase the complexity of the game. For instance, injuries can cause temporary and permanent losses to abilities and attributes in addition to the Life Level damage.
Some activities are abstracted greatly. In the optional rules regarding arrest by police, for instance, the character is given a "chance to escape by getaway". This is simply a saving roll against the character's Evasion value, a failure indicating that the character goes to trial (and the trial is similarly abstract).
Further, there are tables of random complications, intended to be used by the Admin (the game's word for the Referee) in cases where she has not built such into the scenario. These include the results of police investigation, the chance that a target (or someone connected to the target) may attempt revenge, the chances that a message is intercepted or jammed, the chance that a surveillance is discovered, and general occupational hazards such as illness or having one's morals offended. There is even a "Campaign Rules" section that includes some notes toward a type of "domain game", with costs of constructing buildings and setting up a network of agents and contacts.